The present invention relates generally to durable Sb-stabilized phosphate based glass compositions, and more particularly, to Sb-stabilized Mo+W phosphate based glass compositions exhibiting a low glass transition temperature (Tg), and superior resistance to attack from water, humidity and chemicals.
There is currently a great need for glass compositions having a low glass transition temperature (Tg), from about 250xc2x0 C. to about 450xc2x0 C., good chemical durability such as resistance to attack from acids, and resistance to attack from water and humidity. Because of potentially toxic environmental factors, there is also a need for durable, low Tg glass compositions that can be made lead free without affecting durability properties such as resistance to attack from acids, water, humidity, and the like. Glass compositions that combine good chemical durability with the capability of being formed at low temperatures, i.e. compositions having low Tg, are potentially useful for a host of applications such as refractory adhesives, sealing glass frits, and overcladding material for glass fiber.
The search has been continuous to discover new durable glass compositions exhibiting low Tg and enhanced resistance to attack by water, humidity, and chemicals. Thus, the present invention is directed towards a group of new durable Sb-stabilized Mo+W phosphate based glass compositions that have a low Tg, and superior resistance to attack by water, humidity. and chemicals, and are suitable for use in a variety of applications, such as refractory adhesives, sealing frits, and overcladding material for glass fiber.
Additionally, the preferred Sb-stabilized Mo+W phosphate based glass compositions are essentially lead free. The expression essentially lead free indicates that no material containing a substantial concentration of lead is intentionally included in the glass.
In accordance with the present invention it is provided that the addition of about 0.5 to about 60% Sb2O3 to Mo+W phosphate based glass compositions results in a durable, low Tg glass compositions having unexpectedly improved resistance to attack from water, humidity and acids. The durable, low Tg Sb-stabilized Mo+W phosphate based glass compositions of the instant invention preferably comprise, in mole percent (mol %) on the oxide basis, 0-40% R2O where R includes the alkali metals (Li, Na, K, Rb or Cs) as well as Ag and Tl, 0-20% XO where X includes the alkaline earth metals (Mg, Ca, Sr or Ba) as well as Cu, Zn, Cd and Pb, 15-80% MoO3+WO3, 0.5-60% Sb2O3, and 10-40% P2O5. Additionally, the Sb-stabilized Mo+W phosphate based glass composition can contain a total of 0-5%, in mole percent (mol %) on the oxide basis, of glass forming oxides including, but not limited to, B2O3, Al2O3, SiO2, TeO2, Ga2O3, GeO2, transition metal and rare earth metal oxides or mixtures thereof. In a preferred embodiment, the Sb-stabilized Mo+W phosphate based glass compositions are essentially lead free.
Additional features and advantages of the invention will be set forth in the detailed description that follows, and in part, will be readily apparent or recognized to those skilled in the art by practicing the invention as described herein.
It is to be understood that both the foregoing general discussion and the following detailed description and examples provided herein are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed.